Method and apparatus for performing phase detection and timing recovery for a vestigial sideband receiver

Abstract

A method and apparatus for performing phase detection and timing recovery for a vestigial sideband (VSB) signal by processing a complex valued passband VSB signal using a high order non-linearity to detect the phase of the VSB signal. As such, an all digital solution to timing recovery for a high definition television is provided.

What is claimed is:  
     
       1. A timing recovery apparatus comprising: 
       a frequency shifter;  
       a polyphase interpolation filter connected to the frequency shifter;  
       a bandedge prefilter connected to the polyphase interpolation filter;  
       a phase detector, connected to the bandedge filter, having a fourth order nonlinearity;  
       a loop filter connected to the phase detector; and  
       a numerically controlled oscillator connected to the loop filter and connected to the polyphase interpolation filter.  
     
     
       2. The apparatus of  claim 1  wherein the output of the phase detector is real valued. 
     
     
       3. The timing recovery apparatus of  claim 1  wherein the fourth order nonlinearity is defined by 
       
         
             v ( t )= g   + ( t )× g   −   * ( t )  
         
       
       
         
             y ( t )= sgn ( Re{v ( t )})× Im{v ( t )} 
         
       
       where y(t) is an output of the phase detector, g(t) is a complex valued prefilter output for an upper bandedge, g(t) is a prefilter output for a lower bandedge. 
     
     
       4. The timing recovery apparatus of  claim 1  wherein the bandedge prefilter produces a lower complex bandedge signal and an upper complex bandedge signal and said phase detector comprises: 
       a complex conjugate block for producing a complex conjugate of the lower complex bandedge signal;  
       a complex multiplier for multiplying the complex conjugate of the lower complex bandedge signal with the upper complex bandedge signal producing a multiplied signal;  
       an imaginary extractor for extracting the imaginary component of the multiplied signal;  
       a real extractor for extracting a real component of the multiplied signal;  
       a signum function block for applying a signum function to the real component of the multiplied signal; and  
       a real multiplier for multiplying an output of signum function block with the imaginary component of the multiplied signal to produce a phase error signal.  
     
     
       5. A high definition television comprising: 
       a tuner for selecting a vestigial sideband (VSB) signal from a plurality of VSB signals;  
       an analog-to-digital (A/D) converter for digitizing the selected VSB signal;  
       a timing recovery circuit for processing the digitized VSB signal to extract in-phase and quadrature phase components of the VSB signal, where said timing recovery circuit uses a high order nonlinearity to detect the phase of the VSB signal and further comprises:  
       a frequency shifter;  
       a polyphase interpolation filter connected to the frequency shifter;  
       a bandedge prefilter connected to the polyphase interpolation filter;  
       a phase detector, connected to the bandedge filter having a fourth order nonlinearity;.  
       a loop filter connected to the phase detector; and  
       a numerically controlled oscillator connected to the loop filter; and  
       a decoder for extracting data from the in-phase component of the VSB signal.  
     
     
       6. The high definition television of  claim 5  wherein the output of the phase detector is real valued. 
     
     
       7. The high definition television of  claim 5  wherein the phase detector uses a high order nonlinearity defined by 
       
         
             v ( t )= g   + ( t )× g   −   * ( t )  
         
       
       
         
             y ( t )= sgn ( Re{v ( t )})× Im{v ( t )} 
         
       
       where y(t) is an output of the phase detector, g(t) is a complex valued prefilter output for an upper bandedge, g(t) is a prefilter output for a lower bandedge. 
     
     
       8. The high definition television of  claim 7  wherein the bandedge prefilter produces a lower complex bandedge signal and an upper complex bandedge signal and said phase detector comprises: 
       a complex conjugate block for producing a complex conjugate of the lower complex bandedge signal;  
       a complex multiplier for multiplying the complex conjugate of the lower complex bandedge signal with the upper complex bandedge signal producing a multiplied signal;  
       an imaginary extractor for extracting the imaginary component of the multiplied signal;  
       a real extractor for extracting a real component of the multiplied signal;  
       a signum function block for applying a signum function to the real component of the multiplied signal; and  
       a real multiplier for multiplying an output of signum function block with the imaginary component of the multiplied signal to produce a phase error signal.